Electric vehicles in which an electric motor is mounted (including hybrid vehicles) drive the electric motor by using electric power stored in a secondary battery. Regenerative braking is a function specific to these electric vehicles. With regenerative braking, an electric motor is caused to function as a power generator during braking of a vehicle, to thereby convert kinetic (motion) energy of the vehicle to electric energy for performing braking. Further, the electric energy that is obtained is supplied to a secondary battery for charging and is reused at the time of acceleration or the like.
Here, in order to efficiently store, in the secondary battery, the electric power generated during the regenerative braking, the secondary battery should have a sufficient capacity. It is therefore desirable to control the electric power stored in the secondary battery such that the secondary battery can receive the regenerative electric power or the secondary battery can supply the electric power to the electric motor upon request.
For example, Patent Literature 1 discloses a device for controlling charging/discharging of a secondary battery, which includes a temperature detection section which detects the temperature of a secondary battery, and a charging/discharging electric power control section that controls the charging/discharging electric power such that an upper limit value of the charging/discharging electric power which varies in accordance with a predetermined temperature is not exceeded, when the detected temperature is a predetermined temperature or lower.
Also, Patent Literature 2 discloses a device for controlling charging/discharging of a secondary battery, which includes a temperature detection unit which detects the temperature of a secondary battery, a stored electricity amount detection unit which detects the amount of electricity stored in the secondary battery, a charging/discharging electric power limitation unit which controls the charging/discharging electric power such that the charging/discharging electric power does not exceed a predetermined charging/discharging electric power upper limit value based on the detected temperature and the amount of stored electricity which is detected, for example.
Further, Patent Literature 3 discloses a device for controlling charging/discharging of a secondary battery, which includes an estimation unit which estimates the temperature of a secondary battery, and a limitation unit which limits the charging/discharging electric power of the secondary battery based on the estimated temperature of the secondary battery, for example.
In addition, Patent Literature 4 discloses a charging/discharging control device, which includes a charging/discharging suppression unit which estimates an amount of heat generated by each unit cell after elapse of a predetermined time period based on charging/discharging electric current flowing in a group of batteries, determines whether or not the estimated amount of generated heat exceeds a predetermined value, and, when determining that the predetermined value is exceeded, suppresses the charging/discharging electric power flowing in the group of batteries, for example.
Moreover, Patent Literature 5 discloses a charging/discharging control device, which includes a detection section which detects an operation state of an air conditioning device which is used for temperature adjustment of a battery, and a setting unit which sets a limit value of a charging amount or a discharging amount with respect to the battery in accordance with the operation state.